With the recent progress of semiconductor technology, efforts are made in order to realize the remarkable miniaturization of mechanical structures by using semiconductor technology, and electro-mechanical conversion elements such as micro-actuators or the like are now spotlighted. Such elements are capable of realizing the manufacture of small-sized highly accurate mechanism components, and greatly improving the productivity with use of a semiconductor process. Particularly, micro-actuators using piezoelectric elements are applied to the micro-displacement elements of a scanning tunnel microscope, and actuators for delicate positioning such as the head slider of a magnetic disk drive unit.
For example, in a magnetic disk drive unit, efforts are made as described below. Usually, a magnetic head for recording and reproducing of information on a magnetic disk is mounted on a head slider and fitted to an actuator arm. The actuator arm is rocked by means of a voice coil motor (hereinafter called VCM) and positioned to a specified track position on the magnetic disk, thereby recording and reproducing the information with the magnetic head. However, as the recording density is increased, it is now difficult to assure sufficient accuracy by using only such a conventional VCM for positioning. Accordingly, in addition to the positioning means of VCM, a technology of high-speed and highly accurate positioning that can be realized by fine driving of a head slider with use of a fine positioning means using piezoelectric elements is proposed. [For example, extra-high TPI and piggy-back actuators (IDEMA Japan News No. 32, pp 4-7, by International Disk Drive Association)].
As described above, various applications of actuators using piezoelectric elements are expected, but multilayer configurations such as a green sheet laminate system or a thick film multilayer system have been conventionally employed in particular (for example, Japanese Laid-open Patent H6-224483). However, one layer of a piezoelectric element manufactured by such method is about several 10 μm in thickness, and therefore, it requires a driving voltage of about 100V.
As a method for solving this problem, Japanese Laid-open Patent No. H8-88419 discloses a thin film laminate type actuator that is small-sized, is driven with a low voltage, and has a large amount of displacement. Its manufacturing method is also described. That is, an electrode layer of platinum or the like, a piezoelectric layer made up of piezoelectric material such as lead zirconate titanate (PZT), an electrode layer, and a bonding layer made up of glass or silicon are in that order evaporated on a mono-crystalline substrate of magnesium oxide or the like, thereby forming a piezoelectric member. Piezoelectric members thus formed are bonded to each other by an anode bonding method, and the substrate at the side of further lamination is removed by grinding or the like, and a bonding layer is formed on the electrode layer then exposed. After that, a step of bonding the bonding layer to the bonding layer of another piezoelectric member according to the procedure as described above is repeated to form a laminate body. After that, inner layer electrodes are alternately taken out from both sides in order to obtain a laminate type actuator. Also, as a method of bonding piezoelectric members to each other, it is disclosed that a surface activation bonding method and an adhesive application bonding method may also be employed in addition to the anode bonding method. However, in this manufacturing method, since an external electrodes is formed from two sides of a laminate body, with a piezoelectric member laminatee thereon, via an insulating layer, it is necessary to form the external electrode at least for each individual laminate body, and there arises a problem of productivity. Also, the configuration is such that displacement takes place in a direction vertical to the substrate surface, and for example, there arises a problem such that the shape is not suited for internal use as a miniature actuator for the head slider of a magnetic disk drive unit.
Further, Japanese Laid-open Patent No. H11-345833 discloses a manufacturing method for mounting a pyroelectric element and piezoelectric element on a separately disposed electrode forming substrate with good productivity. In this method, an element formed on a temporary substrate with an element transfer jig is fixed at a predetermined position by using resin or double-side adhesive tape or the like, followed by selective etching of only the temporary substrate. Subsequently, an electrode provided on the electrode forming substrate is bonded, by soldering for example, to the electrode of the element which is opposed thereto. After that, the resin or adhesive tape or the like used for fixing the element is removed to separate the element transfer substrate and the element from each other, and thereby, a pyroelectric element and piezoelectric element are formed in a state of being bonded to an electrode forming substrate as specified. Since the element is fixed on the element transfer jig, there is no fear of causing the elements to be deformed or damaged even when the temporary substrate is selectively etched and removed, and it is possible to maintain the specified position and to bond them together onto the electrode forming substrate. However, in this manufacturing method, individually separated elements are bonded, but such a system makes it relatively difficult to execute their individual bonding while accurately positioning the elements on the element transfer substrate, and with decrease in size and increase in the number of electrode terminals, there arises a problem of positional deflection in relation to the electrode forming substrate. Also, the adhesive is required to be a material that may endure the soldering temperature for mounting and also to be a stable adhesive material that can be removed by a specified solution even after being subjected to the temperature.
Accordingly, in a piezoelectric element which is formed on a substrate by laminating a plurality of piezoelectric thin films, held between electrode layers, with use of adhesive, the problems to be solved are to provide a manufacturing method that ensures a high yield and good productivity without characteristics deterioration of each component material, particularly, to manufacture piezoelectric elements with electrodes arranged on same surface in order to realize a piezoelectric actuator in the paired form of two elements and, at the same time, to improve the productivity and provide the products at low costs.